According to an article about him in The Catholic Encyclopedia, Elijah “is honoured by both the Greek and Latin Churches on 20 July.” Although many Catholics (and others) believe that Elijah (or a type of Elijah) will be one of the two witnesses, The Catholic Encyclopedia article about him never mentions that role related to him.
The Bible itself tells about the original Elijah in the books of 1 Kings, 2 Kings, and 2 Chronicles. In his first mention, God has him called for a drought: …